Randomized controlled trials of the efficacy of lung cancer screening by sputum cytology revisited

BACKGROUND:

Two randomized controlled trials of lung cancer screening initiated in the 1970s, the Johns Hopkins Lung Project and the Memorial Sloan‐Kettering Lung Study, compared 1 arm that received annual chest X‐ray and 4‐monthly sputum cytology (dual‐screen) to a second arm that received annual chest X‐ray only. Previous publications from these trials reported similar lung cancer mortality between the 2 groups. However, these findings were based on incomplete follow‐up, and each trial on its own was underpowered to detect a modest mortality benefit.

METHODS:

The authors estimated the efficacy of lung cancer screening with sputum cytology in an intention‐to‐screen analysis of lung cancer mortality, using combined data from these trials (n = 20,426).

RESULTS:

Over ½ of squamous cell lung cancers diagnosed in the dual‐screen group were identified by cytology; these cancers tended to be more localized than squamous cancers diagnosed in the X‐ray only arm. After 9 years of follow‐up, lung cancer mortality was slightly lower in the dual‐screen than in the X‐ray only arm (rate ratio [RR], 0.88; 95% confidence interval [CI], 0.74‐1.05). Reductions were seen for squamous cell cancer deaths (RR, 0.79; 95% CI, 0.54‐1.14) and in the heaviest smokers (RR, 0.81; 95% CI, 0.67‐1.00). There were also fewer deaths from large cell carcinoma in the dual‐screen group, although the reason for this is unclear.

CONCLUSIONS:

These data are suggestive of a modest benefit of sputum cytology screening, although we cannot rule out chance as an explanation for these findings. Cancer 2009. © 2009 American Cancer Society.     

Lung cancer mortality in the Mayo Lung Project: impact of extended follow-up

BACKGROUND: The Mayo Lung Project (MLP) was a randomized, controlled clinical trial of lung cancer screening that was conducted in 9211 male smokers between 1971 and 1983. The intervention arm was offered chest x-ray and sputum cytology every 4 months for 6 years; the usual-care arm was advised at trial entry to receive the same tests annually. No lung cancer mortality benefit was evident at the end of the study. We have extended follow-up through 1996. METHODS: A National Death Index-PLUS search was used to assign vital status and date and cause of death for 6523 participants with unknown information. The median survival for lung cancer patients diagnosed before July 1, 1983, was calculated by use of Kaplan-Meier estimates. Survival curves were compared with the log-rank test. RESULTS: The median follow-up time was 20.5 years. Lung cancer mortality was 4.4 (95% confidence interval [CI] = 3.9-4.9) deaths per 1000 person-years in the intervention arm and 3.9 (95% CI = 3.5-4.4) in the usual-care arm (two-sided P: for difference =.09). For participants diagnosed with lung cancer before July 1, 1983, survival was better in the intervention arm (two-sided P: =.0039). The median survival for patients with resected early-stage disease was 16.0 years in the intervention arm versus 5.0 years in the usual-care arm. CONCLUSIONS: Extended follow-up of MLP participants did not reveal a lung cancer mortality reduction for the intervention arm. Similar mortality but better survival for individuals in the intervention arm indicates that some lesions with limited clinical relevance may have been identified in the intervention arm.     

Finding needles in a haystack: annual low-dose computed tomography screening reduces lung cancer mortality in a high-risk group

Lung cancer is a global health issue. Compared with other common malignancies, the prognosis is poor as many patients present with advanced disease. The National Lung Screening Trial (NLST) aimed to identify and treat early lung cancers using annual low-dose computed tomography (CT) screening in a high-risk group. When compared with chest x-ray screening, low-dose CT screening reduced lung cancer mortality by 20%; the NLST is the first lung cancer screening trial to demonstrate such a mortality benefit. However, we must wait for cost-effectiveness data from the NLST, as well as the results of ongoing European studies comparing low-dose CT with observation alone, before firm conclusions can be drawn regarding the overall benefits of introducing a CT screening program to clinical practice.     

Modeling the mortality reduction due to computed tomography screening for lung cancer

BACKGROUND:

The efficacy of computed tomography (CT) screening for lung cancer remains controversial because results from the National Lung Screening Trial are not yet available. In this study, the authors used data from a single‐arm CT screening trial to estimate the mortality reduction using a modeling‐based approach to construct a control comparison arm.

METHODS:

To estimate the potential lung cancer mortality reduction because of CT screening, a previously developed and validated model was applied to the screening trial to predict the number of lung cancer deaths in the absence of screening. By using age, gender, and smoking characteristics matching those of the trial participants, the model was used to simulate 5000 trials in the absence of CT screening to produce the expected number of lung cancer deaths along with 95% confidence intervals (95% CIs), while adjusting for healthy volunteer bias.

RESULTS:

There were 64 observed lung cancer deaths in the screening cohort (n = 7995), whereas the model predicted 117.7 deaths (95% CI, 98 deaths‐139 deaths), indicating a mortality reduction of 45.6% (P < .001). When a more conservative healthy volunteer adjustment was applied, 111.3 lung cancer deaths were predicted (95% CI, 91 deaths‐132 deaths), for a lung cancer‐specific mortality reduction of 42.5% (P < .001).

CONCLUSIONS:

The results of the current study indicate that CT screening along with early stage treatment can reduce lung cancer‐specific mortality. This mortality reduction is greatly influenced by the protocol of nodule follow‐up and treatment, and the length of follow‐up. Cancer 2011. © 2011 American Cancer Society.     

Death certificates provide an adequate source of cause of death information when evaluating lung cancer mortality: an example from the Mayo Lung Project

To assess the accuracy of death certificates in assigning lung cancer as the underlying cause of death, death certificate data were compared to mortality review committee-determined causes of death among participants in the Mayo Lung Project. Further, the impact of death certificate misclassification on lung cancer mortality rates and Cox proportional hazards models was evaluated. The Mayo Lung Project (1971-1983) was a randomized controlled trial of lung cancer screening; participants were male smokers aged 45 years and older who were seen as outpatients at the Mayo Clinic in Rochester, Minnesota. Overall there were 237 lung cancer deaths according to mortality review, and 224 according to the death certificate (sensitivity 88.6 percent, 95 percent confidence interval (CI) 83.9, 92.4; specificity 99.1 percent, 95 percent CI 98.6, 99.5). As compared to the mortality review committee's determination, the use of death certificate data resulted only in slight decreases to the calculated lung cancer mortality rates for each screening arm, and did not result in appreciable changes to hazard ratios for lung cancer mortality in Cox regression models. In these data, death certificates were sufficiently sensitive and specific such that their use did not result in a meaningful change to mortality-based outcomes.     

Finding needles in a haystack: annual low-dose computed tomography screening reduces lung cancer mortality in a high-risk group

Evaluation of: Aberle DR, Adams AM, Berg CD et al.; National Lung Screening Trial Research Team. Reduced lung-cancer mortality with low-dose computed tomographic screening. N. Engl. J. Med. 365(5), 395–409 (2011).

Lung cancer is a global health issue. Compared with other common malignancies, the prognosis is poor as many patients present with advanced disease. The National Lung Screening Trial (NLST) aimed to identify and treat early lung cancers using annual low-dose computed tomography (CT) screening in a high-risk group. When compared with chest x-ray screening, low-dose CT screening reduced lung cancer mortality by 20%; the NLST is the first lung cancer screening trial to demonstrate such a mortality benefit. However, we must wait for cost–effectiveness data from the NLST, as well as the results of ongoing European studies comparing low-dose CT with observation alone, before firm conclusions can be drawn regarding the overall benefits of introducing a CT screening program to clinical practice.     

Annual or biennial CT screening versus observation in heavy smokers: 5-year results of the MILD trial

The efficacy and cost-effectiveness of low-dose spiral computed tomography (LDCT) screening in heavy smokers is currently under evaluation worldwide. Our screening program started with a pilot study on 1035 volunteers in Milan in 2000 and was followed up in 2005 by a randomized trial comparing annual or biennial LDCT with observation, named Multicentric Italian Lung Detection. This included 4099 participants, 1723 randomized to the control group, 1186 to biennial LDCT screening, and 1190 to annual LDCT screening. Follow-up was stopped in November 2011, with 9901 person-years for the pilot study and 17 621 person-years for Multicentric Italian Lung Detection. Forty-nine lung cancers were detected by LDCT (20 in biennial and 29 in the annual arm), of which 17 were identified at baseline examination; 63% were of stage I and 84% were surgically resectable. Stage distribution and resection rates were similar in the two LDCT arms. The cumulative 5-year lung cancer incidence rate was 311/100 000 in the control group, 457 in the biennial, and 620 in the annual LDCT group (P=0.036); lung cancer mortality rates were 109, 109, and 216/100 000 (P=0.21), and total mortality rates were 310, 363, and 558/100 000, respectively (P=0.13). Total mortality in the pilot study was similar to that observed in the annual LDCT arm at 5 years. There was no evidence of a protective effect of annual or biennial LDCT screening. Furthermore, a meta-analysis of the four published randomized trials showed similar overall mortality in the LDCT arms compared with the control arm.     

Modeling of long-term screening for lung carcinoma.

BACKGROUND: Results from the Mayo Lung Project (MLP), a randomized clinical trial for the early detection of lung carcinoma, were interpreted as proof that the early detection of lung carcinoma by chest X-ray does not reduce the mortality from this disease. Recent analysis of extended follow-up data from the MLP subjects found that after approximately 20 years there still was no apparent difference in lung carcinoma mortality between a study group and a control group. METHODS: To view this result within context, the authors utilized a previously published simulation model of the MLP, with parametric values that were estimated at the time of the original publication based on the data collected by the MLP. RESULTS: The model produced predictions of the extended follow-up statistics that were found to be consistent with the data published in the prior study. The authors believe this provides long-term validation for the model. Conversely, the same model demonstrated that had the study subjects been screened annually for the extended follow-up period, the difference in mortality would be noticeable, even with the low sensitivity of chest X-ray detection. CONCLUSIONS: The results of current study strongly suggest that long-term screening with chest X-ray results in a reduction in lung carcinoma mortality. The limited extent of this benefit is the result of the low sensitivity of chest X-ray as a screening tool.     

Mortality outcomes of low-dose computed tomography screening for lung cancer in urban China: a decision analysis and implications for practice

Background:Mortality outcomes in trials of low-dose computed tomography (CT) screening for lung cancer are inconsistent.This study aimed to evaluate whether CT screening in urban areas of China could reduce lung cancer mortality and to investigate the factors that associate with the screening effect.Methods:A decision tree model with three scenarios (low-dose CT screening,chest X-ray screening,and no screening) was developed to compare screening results in a simulated Chinese urban cohort (100,000 smokers aged 45-80 years).Data of participant characteristics were obtained from national registries and epidemiological surveys for estimating lung cancer prevalence.The selection of other tree variables such as sensitivities and specificities of low-dose CT and chest X-ray screening were based on literature research.Differences in lung cancer mortality (primary outcome),false diagnoses,and deaths due to false diagnosis were calculated.Sensitivity analyses were performed to identify the factors that associate with the screening results and to ascertain worst and optimal screening effects considering possible ranges of the variables.Results:Among the 100,000 subjects,there were 448,541,and 591 lung cancer deaths in the low-dose CT,chest X-ray,and no screening scenarios,respectively (17.2％ reduction in low-dose CT screening over chest X-ray screening and 24.2％ over no screening).The costs of the two screening scenarios were 9387 and 2497 false diagnoses and 7 and 2 deaths due to false diagnosis among the 100,000 persons,respectively.The factors that most influenced death reduction with low-dose CT screening over no screening were lung cancer prevalence in the screened cohort,low dose CT sensitivity,and proportion of early-stage cancers among low-dose CT detected lung cancers.Considering all possibilities,reduction in deaths (relative numbers) with low-dose CT screening in the worst and optimal cases were 16 (5.4％) and 288 (40.2％) over no screening,respectively.Conclusions:In terms of mortality outcomes,our findings favor conducting low-dose CT screening in urban China.However,approaches to reducing false diagnoses and optimizing important screening conditions such as enrollment criteria for screening are highly needed.     

Lung cancer screening with spiral CT: baseline results of the randomized DANTE trial

BACKGROUND: Despite the high survival rates reported for screening-detected cases, the potential of screening of high-risk subjects for reducing lung cancer mortality is still unproven. We herewith present the baseline results of a randomized trial comparing screening for lung cancer with annual spiral computed tomography (CT) versus a yearly clinical review. METHODS: Male subjects, 60-74 years old, and smokers of 20+ pack-years were enrolled. All participants received a baseline medical examination, chest X-rays (CXR) and sputum cytology upon accrual. Subjects randomized in the spiral CT group received a spiral CT scan at baseline, then yearly for the following 4 years. For controls, a yearly clinical examination was scheduled for the following 4 years. RESULTS: 2472 subjects were randomized (1276 spiral CT arm, 1196 controls). Age, smoking exposure and co-morbid conditions were similar in the two groups. In the spiral CT group, 28 lung cancers were detected, 13 of which were visible in the baseline chest X-rays (overall prevalence 2.2%). Sixteen out of 28 tumours (57%) were stage I, and 19 (68%) were resectable. In the control group, eight cases were detected by the baseline chest X-rays (prevalence rate 0.67%), four (50%) were stage I, and six (75%) were resectable. CONCLUSIONS: Baseline lung cancer detection rate in the spiral CT arm was higher than in most published studies. The stage I detection rate was increased four-fold by spiral CT versus chest X-rays. However, more tumours in an advanced stage were also detected by CT. The high resection rate of screening-detected patients suggests a possible increase in cure rate. However, longer follow-up is required for definitive conclusions. This trial has been registered at www.Clinicaltrials.gov, registration No. NCT00420862.     

Lung cancer screening with low-dose computed tomography

Lung cancer is the most common cause of cancer death in the world, with most patients having a dismal prognosis. As many as 40?% of lung cancers are diagnosed in stage IV, with current 5-year survival rates well below 20?%. Conventional chest radiography has been historically derided as a valid screening tool for this dreaded disease. A recent National Cancer Institute-sponsored study known as the Prostate, Lung, Colorectal, and Ovarian cancer screening trial found no benefit from such screening in patients at risk. In recent years, low-dose computed tomography (LDCT) of the chest has emerged as a promising screening tool. Recent evidence from the National Lung Screening Trial (NLST) demonstrated a 20?% reduction in mortality from lung cancer in patients undergoing three rounds of LDCT screening. Opponents of lung cancer screening favor its limited use in the setting of well-designed trials claiming excessive false-positive findings, overdiagnosis, and morbidity and mortality associated with invasive testing. That notwithstanding, leading medical societies such as ASCO and ATS have positioned themselves recently in favor of screening subjects meeting the NLST criteria.     

High incidence of lung cancer after non-muscle-invasive transitional cell carcinoma of the bladder: implications for screening trials

PURPOSE: Lung cancer screening trials depend on the selection of a sufficiently high-risk population. Because not all smokers develop cancer, we hypothesize that a history of tobacco-associated malignancy might more reliably predict for subsequent lung cancer. Because patients with early-stage bladder transitional cell carcinoma (TCC) often have a long survival, we considered whether they would constitute a suitable population for a screening study. PATIENTS AND METHODS: Patients with Ta/is/1 N0 M0 TCC of the bladder and no history of previous cancer treated surgically between 1983 and 2002 were studied using the Surveillance, Epidemiology, and End Results (SEER) database. The incidence and cancer-specific mortality of second nonurothelial solid organ cancers was determined. The standardized incidence ratio (SIR) and 15-year actuarial incidences were determined. RESULTS: From 1983 to 2002, 8300 patients meeting the inclusion criteria were entered into the SEER-9 Registry. Among them, the SIR for a second solid organ malignancy was 1.25 (95% CI, 1.18-1.32). The SIR was significantly increased for tumors of the lung (1.71), head and neck (1.32), and prostate (1.28). The 15-year incidence of and mortality from lung cancer were 8.8% and 8.6%, respectively. Among all nonurothelial second malignancies, lung cancers accounted for 32.5% of the incidence and 53.4% of cancer-specific deaths. Moreover, lung cancer accounted for 12.2% of overall deaths in these patients. CONCLUSIONS: Patients with non-muscle-invasive bladder TCC suffer a high incidence of mortality from lung cancer and might constitute a suitable population for a lung screening trial. Other tobacco-related health events might add to smoking history in identifying high-risk populations.     

Lung Cancer Incidence and Mortality with Extended Follow-up in the National Lung Screening Trial

IntroductionThe National Lung Screening Trial (NLST) randomized high-risk current and former smokers to three annual screens with either low-dose computed tomography (LDCT) or chest radiography (CXR) and demonstrated a significant reduction in lung cancer mortality in the LDCT arm after a median of 6.5 years' follow-up. We report on extended follow-up of NLST subjects.MethodsSubjects were followed by linkage to state cancer registries and the National Death Index. The number needed to screen (NNS) to prevent one lung cancer death was computed as the reciprocal of the difference in the proportion of patients dying of lung cancer across arms. Lung cancer mortality rate ratios (RRs) were computed overall and adjusted for dilution effect, with the latter including only deaths with a corresponding diagnosis close enough to the end of protocol screening.ResultsThe median follow-up times were 11.3 years for incidence and 12.3 years for mortality. In all, 1701 and 1681 lung cancers were diagnosed in the LDCT and CXR arms, respectively (RR = 1.01, 95% confidence interval [CI]: 0.95–1.09). The observed numbers of lung cancer deaths were 1147 (with LDCT) versus 1236 (with CXR) (RR = 0.92, 95% CI: 0.85–1.00). The difference in the number of patients dying of lung cancer (per 1000) across arms was 3.3, translating into an NNS of 303, which is similar to the original NNS estimate of around 320. The dilution-adjusted lung cancer mortality RR was 0.89 (95% CI: 0.80–0.997). With regard to overall mortality, there were 5253 (with LDCT) and 5366 (with CXR) deaths, for a difference across arms (per 1000) of 4.2 (95% CI: –2.6 to 10.9).ConclusionExtended follow-up of the NLST showed an NNS similar to that of the original analysis. There was no overall increase in lung cancer incidence in the LDCT arm versus in the CXR arm.     

Molecular profiling of computed tomography screen-detected lung nodules shows multiple malignant features.

RATIONALE AND PURPOSE: Low-dose spiral computerized axial tomography (spiral CT) is effective for the detection of small early lung cancers. Although published data seem promising, there has been a significant degree of discussion concerning the potential of overdiagnosis in the context of spiral CT-based screening. The objective of the current study was to analyze the phenotypic and genetic alterations in the small pulmonary malignancies resected after detection in the University of Navarra/International Early Lung Cancer Action Project spiral CT screening trial and to determine whether their malignant molecular features are similar to those of resected lung tumors diagnosed conventionally. EXPERIMENTAL DESIGN: We analyzed 17 biomarkers of lung epithelial malignancy in a series of 11 tumors resected at our institution during the last 4 years (1,004 high-risk individuals screened), using immunohistochemistry and fluorescence in situ hybridization (FISH). A parallel series of 11 gender-, stage-, and histology-matched lung cancers diagnosed by other means except screening was used as control. RESULTS: The molecular alterations and the frequency of phenotypic or genetic aberrations were very similar when screen-detected and nonscreen-detected lung cancers were compared. Furthermore, most of the alterations found in the screen-detected cancers from this study were concordant with what has been described previously for stage I-II lung cancer. CONCLUSIONS: Small early-stage lung cancers resected after detection in a spiral CT-based screening trial reveal malignant molecular features similar to those found in conventionally diagnosed lung cancers, suggesting that the screen-detected cancers are not overdiagnosed.     

Modeling excess lung cancer risk among screened arm participants in the Mayo Lung Project

BACKGROUND:

The Mayo Lung Project (MLP) was a randomized clinical trial designed to test whether periodic screening by chest x‐ray reduced lung cancer (LC) mortality in men who were high‐risk smokers. Among MLP participants, there were more deaths from LC in the screening arm both at the trial's end and after long‐term follow‐up. Overdiagnosis was cited widely as an explanation for the MLP results, whereas a role for excess LC risk attributable to undergoing numerous chest x‐ray screenings largely was unexamined. The authors of this report examined the consistency of the MLP data with a modified 2‐stage clonal expansion (TSCE) model of excess LC risk.

METHODS:

By using a simulation model calibrated to the initial MLP data, the authors examined the expected statistical variance of LC incidence and mortality between the screening and control arms. A Bayesian estimation framework using a modified version of the TSCE model to evaluate the role of excess LC risk attributable to chest x‐ray screening was derived and applied to the MLP data.

RESULTS:

Simulation experiments indicated that the overall difference in LC deaths and incidence between the study arm and the control arm was unlikely (P = .0424 and P = .0104, respectively) assuming no excess risk of LC. The authors estimated that the 10‐year excess LC risk for a man aged 60 years who smoked and who received 10 chest x‐ray screenings was 0.574% (P = .0021).

CONCLUSIONS:

The excess LC risk observed among screening arm participants was found to be statistically significant with respect to the TSCE model framework in part because of the incorporation of key risk correlates of age and screen frequency into the estimation framework. Cancer 2010. Published 2010 American Cancer Society     

Lung cancer screening: an emerging cancer control issue presents opportunities for an awareness campaign in rural Michigan

Lung cancer is the leading cause of cancer deaths in the United States representing about 25% of all cancer deaths. The risk from smoking has increased over time with racial/ethnic minorities and disadvantaged populations having higher smoking rates and experiencing greater burden of lung cancer compared to other populations. Rural populations, in particular, experience higher rates of tobacco usage associated with increased incidence of lung cancer. National efforts to identify lung cancer in its early stage would greatly benefit high-risk populations, consequently reducing advanced cancers and potentially decreasing smoking rates. In 2013, lung cancer screening with low-dose computed tomography was recommended by the US Preventive Services Task Force for early detection of lung cancer. These guidelines were developed after the results of the National Lung Screening Trial. The National Lung Screening Trial study showed a 20% reduction in deaths of participants who were current or former heavy smokers who were screened with low-dose computed tomography versus those screened by chest X-ray. In response to this evidence and using state lung cancer burden data and local smoking rates as a guide, Michigan implemented a lung cancer screening awareness campaign in the rural northern, lower peninsula. Awareness of lung cancer screening was increased through the use of a variety of media including gas station/convenience store small media, digital media, radio broadcast media, and the use and marketing of a website that provided lung cancer screening information and resources.     

Impact of low-dose CT on lung cancer screening

Despite advances in therapy, the prognosis of lung cancer remains dismal due to the fact that most cases of lung cancer are diagnosed at advanced stages, when the chance of cure is poor. In cases detected at early stages prognosis is better. Unfortunately, early lung cancer usually causes no symptoms and is, consequently, rarely diagnosed. Therefore, screening for early asymptomatic lung cancer with diagnostic procedures appears promising particularly as risk factors for lung cancer are well known (cigarette smoking, occupational asbestos exposure and others) and screening could, therefore, focus on these risk groups. In the past, screening trials using analysis of sputum cytology and to some extent chest radiography have failed to demonstrate a reduction in lung-cancer mortality with screening, probably due to insufficient sensitivity of these tests for early lung cancer. During the last decade the introduction of spiral computed tomography (CT) has provided a technique with a much higher sensitivity for small lung cancers. Feasibility studies using low-radiation-dose CT demonstrated a high proportion of non-small-cell lung cancer at the initial examination (prevalence) with decreasing numbers of detected cancers at follow-up (incidence). The proportion of early-stage tumors was high both at prevalence and incidence examinations. The rate of invasive procedures for benign lesions was low; most indeterminate lesions could be classified with non-invasive diagnostic approaches. The proportion of interval cancers (cancers diagnosed by symptoms between two screening CT scans) was low. As, however, these one-arm feasibility trials are not appropriate to assess a potential mortality reduction through CT screening, prospective randomised multicenter trials were recently initiated in several countries to analyse the effect of CT screening on lung-cancer mortality.     

Overdiagnosis in chest radiographic screening for lung carcinoma: frequency

BACKGROUND: The pattern of results in the Mayo Lung Project (MLP), which is the basis for the prevailing recommendations against radiographic screening for lung carcinoma, has led to the assertion that up to 50% of the diagnosed cases of early-stage disease in that trial may have represented overdiagnosed, indolent cases. This finding suggests the possibility of such a high frequency of overdiagnosis in chest radiographic lung carcinoma screening in general. In the current study, the authors analyzed data from the MLP and its counterpart study at Memorial Sloan-Kettering Cancer Center (MSK) to estimate the frequency of overdiagnosis in these studies. METHODS: For the cases diagnosed as Stage I in the MLP and the MSK studies, the doubling times of tumor volumes were calculated. The calculations were based on size measurements recorded by the original investigators from chest radiographs taken during the course of each study. RESULTS: The median doubling times were 101 days in the MLP and 144 days in the MSK, times that are somewhat shorter than those reported in published series of adenocarcinoma cases diagnosed outside screening, and only 5% had doubling times exceeding 400 days. CONCLUSIONS: The hypothesis that early-stage lung tumors diagnosed on chest radiography during lung carcinoma screening may frequently be overdiagnosed, indolent cases needs to be rejected.     

Lung cancer screening

Lung cancer is the primary cause of cancer mortality in developed countries. First diagnosis only when disease has already reached the metastatic phase is the main reason for failure in treatment. To this regard, although low-dose spiral computed tomography (CT) has proven to be effective in the early detection of lung cancer (providing both higher resectability and higher long-term survival rates), the capacity of annual CT screening to reduce lung cancer mortality in heavy smokers has yet to be demonstrated. Numerous ongoing large-scale randomised trials are under way in high-risk individuals with different study designs. The initial results should be available within the next 2 years.     

Computed tomography screening for the early detection of lung cancer

Although lung cancer is the leading cause of cancer-related death in the world and has an increased chance of cure if detected at an earlier stage, routine lung cancer screening is currently not recommended in the United States. Unfortunately, most patients with lung cancer present only after the onset of symptoms and have advanced disease that cannot be surgically resected. The overall 5-year survival rate for all patients with lung cancer is only 15%. When the cancer is detected at its earliest stage (pathologic stage IA), however, the 5-year survival rate is more than 70%. Although past randomized screening trials evaluating the use of standard chest radiography or sputum cytology have not resulted in lower mortality, recent studies suggest that computed tomography (CT) may have promise as a screening tool. This article summarizes experience over the past decade of using low-dose spiral CT imaging as a screening tool to detect early lung cancers in asymptomatic, high-risk individuals.